Figure 1: Treatment of serum-starved WI-38 cells (3 days) with serum for 2 days induces Rb protein expression, as detected by the PathScan<sup>®</sup> Total Rb Sandwich ELISA Kit #12915. The absorbance readings at 450 nm are shown in the top figure while the corresponding western blot using Rb (D20) Rabbit mAb #9313 is shown in the bottom figure.